U.S. patent application number 11/606295 was filed with the patent office on 2007-05-31 for numerical control system.
This patent application is currently assigned to FANUC LTD. Invention is credited to Yasuharu Aizawa, Kazunari Aoyama, Kunitaka Komaki, Mitsuo Kurakake.
Application Number | 20070120516 11/606295 |
Document ID | / |
Family ID | 37806170 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070120516 |
Kind Code |
A1 |
Kurakake; Mitsuo ; et
al. |
May 31, 2007 |
Numerical control system
Abstract
A numerical control system with shortened communication paths to
lower a cost of the system. A plurality of servo amplifiers for
respectively controlling a plurality of servomotors are arranged
separately from a numerical controller. Pulse encoders for
detecting positions/velocities of the servomotors are connected to
the numerical controller by optical cables forming a serial
communication path in a daisy chain, via a branch unit. The servo
amplifiers for driving the servomotors are connected to the
numerical controller by optical cables in a daisy chain, via the
branch unit. Since the communication path for transmitting signals
from the pulse encoders connects the pulse encoders and the
numerical controller without the servo amplifiers intervened in
between, the communication path is not elongated even in a case of
the servo amplifiers are located remote from the servomotors, to
construct the system with a low cost.
Inventors: |
Kurakake; Mitsuo; (Tokyo,
JP) ; Aoyama; Kazunari; (Yamanashi, JP) ;
Komaki; Kunitaka; (Yamanashi, JP) ; Aizawa;
Yasuharu; (Yamanashi, JP) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
FANUC LTD
Yamanashi
JP
|
Family ID: |
37806170 |
Appl. No.: |
11/606295 |
Filed: |
November 30, 2006 |
Current U.S.
Class: |
318/625 ;
318/569 |
Current CPC
Class: |
G05B 2219/33226
20130101; G05B 2219/40237 20130101; G05B 19/4142 20130101; G05B
2219/33168 20130101 |
Class at
Publication: |
318/625 ;
318/569 |
International
Class: |
G05B 11/32 20060101
G05B011/32 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2005 |
JP |
346377/2005 |
Claims
1. A numerical control system comprising: a numerical controller; a
plurality of servo amplifiers arranged separately from said
numerical controller and connected to said numerical controller; a
plurality of servomotors driven by said servo amplifiers and having
detectors respectively provided for detecting position and/or
velocity of the servomotor; and a serial communication path in a
daisy chain for connecting the detectors respectively provided in
said servomotors to said numerical controller.
2. A numerical control system according to claim 1, wherein said
serial communication path comprises an optical communication
path.
3. A numerical control system according to claim 1, wherein said
serial communication path directly connects the detectors
respectively provided in said servomotors to said numerical
controller.
4. A numerical control system according to claim 1, wherein said
numerical controller and said servo amplifiers are connected by a
serial communication line in a daisy chain via a branch unit, and
said serial communication path connects the detectors respectively
provided in said servomotors to said numerical controller via the
branch unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a numerical control system
for controlling a plurality of servomotors.
[0003] 2. Description of Related Art
[0004] In a numerical control system for controlling a plurality of
servomotors, a numerical controller and amplifiers for driving
respective servomotors are connected by electric cables, and
signals from detectors provided at the respective servomotors for
detecting positions/velocities of the servomotors are fed back to
the numerical controller that performs feedback control of
positions/velocities of the respective servomotors. In some
systems, the servo amplifiers for driving the respective
servomotors are provided within the numerical controller so that
outputs from the servo amplifiers are fed to the respective
servomotors (see JP 7-49708A, JP 10-275006A).
[0005] However, since the servo amplifiers include inverters for
controlling electric power to the servomotors, signal processing
sections of the numerical controller are influenced by noises made
by switching actions of the inverters. To cope with this problem,
there have been adopted a system in which the servo amplifiers are
placed at a power circuitry section provided separately from the
numerical controller so that the numerical controller and the servo
amplifiers are separated.
[0006] FIG. 2 shows an example of a conventional numerical control
system in which a numerical controller and servo amplifiers are
arranged separately.
[0007] A numerical controller 1 and servo amplifiers A1, A2, A3, .
. . are connected in a daisy chain by electric or optical
communication cables 2. The servo amplifiers A1, A2, A3, . . . are
respectively connected to servomotors M1, M2, M3, . . . by electric
power cables 5, and to pulse encoders P1, P2, P3, . . . for
detecting positions/velocities of the servomotors M1, M2, M3, . . .
by communication cables 6.
[0008] The positions/velocities detected by the pulse encoders P1,
P2, P3, . . . are fed back to the numerical controller 1 through
the communication cables 6, the servo amplifiers A1, A2, A3, . . .
, and the electric or optical communication cables 2. The numerical
controller 1 performs position/velocity feedback controls based on
command positions/velocities and the fed back positions/velocities
to output driving commands to the respective servo amplifiers A1,
A2, A3, . . . . The servo amplifiers A1, A2, A3, . . . control
electric currents to flow windings of the respective servomotors
M1, M2, M3, . . . by means of inverters so that the servomotors M1,
M2, M3, . . . are drivingly controlled.
[0009] As described above, in the case where the servo amplifiers
A1, A2, A3, . . . are arranged separately from the numerical
controller 1, the signals from the pulse encoders P1, P2, P3, . . .
are fed back to the numerical controller 1 via the servo amplifiers
A1, A2, A3, . . . and the electric or optical communication cables
2 connected to the numerical controller 1.
[0010] In dependence on a structure and/or an installing place of a
machine to be controlled, there is a case where the servo
amplifiers A1, A2, A3, . . . and the servomotors M1, M2, M3, . . .
have to be placed remote from each other. In such case, the signal
paths between the servo amplifiers A1, A2, A3, . . . and the
servomotors M1, M2, M3, . . . have to be elongated so that long
communication cables 6 respectively for the servomotors M1, M2, M3,
. . . are required to be laid, to increase a system cost and a
burden of laying the cables.
SUMMARY OF THE INVENTION
[0011] The present invention provides a numerical control system
capable of shortening communication paths to lower a system
cost.
[0012] A numerical control system of the present invention
comprises: a numerical controller; a plurality of servo amplifiers
arranged separately from the numerical controller and connected to
the numerical controller; a plurality of servomotors driven by the
servo amplifiers and having detectors respectively provided for
detecting position and/or velocity of the servomotors; and a serial
communication path in a daisy chain for connecting the detectors
respectively provided in the servomotors to the numerical
controller.
[0013] The serial communication path may comprise an optical
communication path. The serial communication path may directly
connect the detectors respectively provided in the servomotors to
the numerical controller.
[0014] The numerical controller and the servo amplifiers may be
connected by a serial communication line in a daisy chain via a
branch unit, and the serial communication path may connect the
detectors respectively provided in the servomotors and the
numerical controller via the branch unit.
[0015] With the above configuration, the signals from the detectors
for detecting positions/velocities of the servomotors are sent to
the numerical controller through the serial communication path in a
daisy chain without passing through the servo amplifiers, so that
the communication path for feeding back the detected signals to the
numerical controller is not so elongated even in a case where the
servo amplifiers and the servomotors have to be located remote from
each other, to enable construction of the numerical control system
with a low cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic diagram of a numerical control system
according to an embodiment of the present invention; and
[0017] FIG. 2 is a schematic diagram of a conventional numerical
control system.
DETAILED DESCRIPTION
[0018] FIG. 1 shows an numerical control system according to an
embodiment of the present invention. In FIG. 1, servo amplifiers
A1, A2, A3, . . . are connected to a numerical controller 1 by
optical cables 2 which make a serial communication path in the form
of a daisy chain, via a branch unit 4. The servo amplifiers A1, A2,
A3, . . . respectively drive servomotors M1, M2, M3, . . . through
electric power cables 5. The servomotors M1, M2, M3, . . . are
provided with pulse encoders P1, P2, P3, . . . for detecting
positions/velocities of the servomotors M1, M2, M3, . . . ,
respectively. The pulse encoders P1, P2, P3, . . . are connected to
the numerical controller 1 by optical cables 3 which make a serial
communication path in the form of a daisy chain, via the branch
unit 4.
[0019] The numerical controller 1 sends signals for controlling
positions/velocities of the servomotors M1, M2, M3, . . . to the
servo amplifiers A1, A2, A3, . . . through the optical cables 2
forming the serial communication path, via the branch unit 4. The
servo amplifiers A1, A2, A3, . . . receive the control signals from
the numerical controller 1 and control driving currents to the
servomotors M1, M2, M3, . . . by means of inverters, etc. to
drivingly control the servomotors M1, M2, M3, . . . through the
electric power cables 5. The signals of positions/velocities from
the pulse encoders P1, P2, P3, . . . provided at the servomotors
M1, M2, M3, . . . are fed back to the numerical controller 1
through the optical cables 3 forming the serial communication path
in a daisy chain, via a branch unit 4. The numerical controller 1
performs position/velocity feedback controls based on command
values commanded by a machining program, etc. and the fed back
signals of positions/velocities to output driving commands to the
servo amplifiers A1, A2, A3, . . . .
[0020] The numerical control system according to the embodiment of
the present invention is different from the conventional system as
shown in FIG. 2 in that the signals from the pulse encoders P1, P2,
P3, . . . are fed back to the numerical controller 1 by the optical
cables 3 forming the daisy-chain communication path via the branch
unit 4 according to the embodiment of the invention, whereas the
signals from the pulse encoders P1, P2, P3, . . . are sent to the
servo amplifiers A1, A2, A3, . . . through the electric
communication cables 6 and fed back to the numerical controller 1
through the optical communication cables 2 in the conventional
system. The cables for connecting the servo amplifiers A1, A2, A3,
. . . and the pulse encoders P1, P2, P3, . . . are unnecessary in
the embodiment of the invention, and thus in the case where the
servo amplifiers A1, A2, A3, . . . and the servomotors M1, M2, M3,
. . . have to be placed at remote locations, the numerical
controller 1 and the pulse encoders P1, P2, P3, . . . are connected
by the optical cables 3 forming the communication path of a daisy
chain without the cables for connecting the servo amplifiers and
the pulse encoders to enable constitution of the numerical control
system with a low cost, in comparison with the conventional system
where the cables 6 for connecting the servo amplifiers A1, A2, A3,
. . . and the pulse encoders P1, P2, P3, . . . have to be elongated
in such case.
[0021] In the above embodiment, the optical cables 2 and 3 forming
the serial communication paths are connected to the numerical
controller 1 via the branch unit 4, however, the branch unit 4 does
not necessarily have to be provided so that the optical cables 2
and 3 may be directly connected to the numerical controller 1.
* * * * *